1. Field
The invention relates to an optical component comprising one or two substrates, one or more orientation layers on each substrate, and one or more anisotropic films of cross-linked liquid crystalline monomers or oligomers with locally different orientation of the liquid crystal molecules on the substrate or between the substrates. The invention also relates to the production and use of such components.
2. Description
Anisotropic transparent or colored polymer network layers with highly-resolved pre-set three-dimensional orientation of the optical axis are of great importance in display technology, integrated optics and prevention of forgery.
EP-A-545 234 discloses liquid crystal cells with fine structures comprising regions with defined different orientation and consequently different refractive indices. Refractive index patterns of this kind in a liquid crystal are produced by micromechanically generating a line structure on the surface of the orientation layer bounding the liquid crystal using a stylus moving in correspondence with the scanning pen of a scanning force microscope (scanning probe or atomic force microscope "AFM"!). Depending on the pressure exerted by the stylus, the lines can consist of relatively pronounced grooves or mere of strings of uniformly aligned molecules. In the following description, the term "scratching" is used for the process of producing a line structure by means of a stylus. In a cell of plates structured in this manner, the pattern on the orientation layer constitutes an orientation pattern which is transferred to the liquid crystal. Optically non-linear liquid crystalline or optionally frozen-in optical waveguide structures are important applications.
European Patent Publication No. 611 981, corresponding to U.S. application Ser. No. 08/194,234, which is commonly owned with the present application, the contents of which are herein incorporated by reference discloses materials and methods of stabilizing orientation structures in monomeric liquid crystals by cross-linking. The orientation structures in the liquid crystal are induced by orientation layers of a photo-orientatable polymer network ("PPN layers"). To this end, in a first step the desired pattern is generated photochemically with polarized light in the PPN orientation layer and in a second step is transferred to a liquid crystal layer deposited thereon by spin coating (the "PPN method"). The liquid crystal structure is then stabilized by cross-linking. A cross-linked liquid crystal layer of this kind will hereinafter be called LCP ("liquid crystal polymer") for short.
European Patent Publication No. 689 084, corresponding to U.S. application Ser. No. 08/489,865, which is commonly owned with the present application, the contents of which are herein incorporated by reference, describes optical components having a layer structure of a number of PPN orientation layers and anisotropic layers of cross-linked liquid crystalline monomers. All of these are subject to the limitations of the PPN method, for example, limited resolution, only slightly variable direction of director and limited control of tilt angle.
The not yet published Swiss Patent Application No. 2036/95, corresponding to U.S. application Ser. No. 08/667,687, which is commonly owned with the present application, the contents of which are herein incorporated by reference, describes the production and use of optical components for use as masks, such as for transferring a polarization pattern to a polarization-sensitive layer.
European Patent Publication No. 689 065, which is commonly owned with the present application, corresponding to U.S. application Ser. No. 08/489,866, the contents of which are herein incorporated by reference, describes optical PPN components with a layer structure and the production thereof. Such components are particularly suitable for use against forgery.
It has now been found that the use of cross-linkable liquid crystals together with micromechanically scratched orientation layers can result in structures having much better or even completely new properties.